<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
'Null','Undefined','String','Boolean','Number','Symbol'
<script>
  function sleep(sleepTime){
    for(var start = +new Date;+new Date - start<sleepTime;){}
  }
  var t1 =  +new Date();
  sleep(3000);
  var t2 = +new Date();
  console.log(t2-t1);
</script>
</body>
</html>
